sbuild fails to install build-essential in debian unstable chroot

Trying to build a package in a debian unstable chroot using Bionic sbuild fails due to missing dpkg-scanpackage:
$ sudo sbuild -d unstable -A -s

....

+------------------------------------------------------------------------------+
| Install build-essential |
+------------------------------------------------------------------------------+

Setup apt archive
-----------------

Merged Build-Depends: build-essential, fakeroot
Filtered Build-Depends: build-essential, fakeroot
dpkg-deb: building package 'sbuild-build-depends-core-dummy' in '/<<BUILDDIR>>/resolver-8rjiMc/apt_archive/sbuild-build-depends-core-dummy.deb'.
Can't exec "dpkg-scanpackages": No such file or directory at -e line 23.
system dpkg-scanpackages . /dev/null failed: -1 at -e line 23.
E: cannot create dummy archive
Failed to run apt-ftparchive.
E: Setting up apt archive failed

Setup apt archive
-----------------

Merged Build-Depends: dose-distcheck
Filtered Build-Depends: dose-distcheck
dpkg-deb: building package 'sbuild-build-depends-dose3-dummy' in '/<<BUILDDIR>>/resolver-8rjiMc/apt_archive/sbuild-build-depends-dose3-dummy.deb'.
Can't exec "dpkg-scanpackages": No such file or directory at -e line 23.
system dpkg-scanpackages . /dev/null failed: -1 at -e line 23.
E: cannot create dummy archive
Failed to run apt-ftparchive.
E: Setting up apt archive failed
E: Failed to explain bd-uninstallable

This looks like dpkg-scanpackages is needed to create the dummy package, but that's in dpkg-dev which is what it should be installing at this point.

This used to work before the buster release.

If I pre-install dpkg-dev in the chroot then it works fine.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: sbuild 0.75.0-1ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-46.49-generic 4.15.18
Uname: Linux 4.15.0-46-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Aug 1 02:24:01 2019
PackageArchitecture: all
SourcePackage: sbuild
UpgradeStatus: No upgrade log present (probably fresh install)